The third-order optical nonlinearity of the pyrochlore phase 0.7Pb(Mg _1/3Nb_2/3)O₃-0.3PbTiO₃ thin film on quartz

The xPb(Mg_1/3Nb_2/3)O₃-(1-x)PbTiO ₃ (PMNT) (with x=0.7) thin film is prepared on quartz substrates prepared using a sol-gel process. The PMNT thin film has a well-crystallized pyrochlore phase structure. The sign and magnitude of both real and imaginary parts of third-order nonlinear susceptibility χ(3) of the thin film have been determined by the Z-scan technique performed at 800 nm with a femtosecond laser. The nonlinear refraction index coefficient γ, the nonlinear absorption coefficient β of the thin film are 1.37×10^-12 cm²/W and -6.73×10^-8 m/W, respectively. The real and imaginary part of the third-order nonlinear susceptibility of the film are 1.06×10^-17 and -1.65×10^-19 m ²/V², respectively. The results suggested that the nonlinearity is dominated by the refractive for the film.